Before stepping out of the Pirs docking compartment, the two spacewalkers read measurements of abnormally high levels of carbon dioxide inside their suits.

They were both wearing new, updated versions of the traditional Russian Orlan suits used for spacewalking, which had been fitted with different electronic control systems and more adjustability in the leg, torso and arm regions for comfort.

After a series of checks, Russian mission control decided the readings reflected faulty data, and not actual high levels of carbon dioxide, and gave the spacewalkers a "go" to proceed.

Mission controllers checked in with the spacewalkers throughout the morning to make sure they were not experiencing symptoms of excess carbon dioxide.

"I breathe normally and I feel OK," Barratt reported about an hour into the spacewalk, which officially started at 3:52 a.m. EDT (0752 GMT), about an hour later than planned.

Padalka and Barratt arrived at the orbital laboratory in March on a Russian Soyuz spacecraft to begin a six-month stay.

They are currently serving alongside Japanese astronaut Koichi Wakata, cosmonaut Roman Romanenko, Belgian astronaut Frank De Winne, and Canadian spaceflyer Robert Thirsk.

The latter three arrived last week on a Russian Soyuz flight; collectively, the spaceflyers make up the station's first six-person crew (doubled from the previous crew size of three).

Wakata assisted with today's spacewalk from inside the station.

After the rocky start, Barratt and Padalka worked tirelessly to install two sets of antennas and connect each to a series of power cables. The antennas are intended to help the approaching Mini Research Module 2 gauge its distance and angle when approaching the station after the module launches on an unmanned Russian Soyuz vehicle.

After attaching the antennas and cables, Barratt climbed aboard the long Strela extension pole to survey his handiwork.

While Padalka turned a crank to extend the boom, Barratt snapped photos of the antennas from multiple vantage points for Russian mission control to analyze to make sure they're installed correctly.

"The earth is so beautiful, it's a great view from here," Barratt said as they crossed over South America.

The same two spacewalkers plan a second, shorter spacewalk June 10 to change out a cover on a port of the Zvezda service module, where the new compartment will be installed. Today's excursion was Padalka's seventh spacewalk and Barratt's first.